1. Field of the Invention
The present invention generally relates to a power control method and a power control system using the same and, more particularly, to a method of hybrid power management and a system of hybrid power management, in which one of different output power modes is selected according to a characteristic value output from a fuel cell module.
2. Description of the Prior Art
The fuel cell has attracted tremendous attention as an alternative energy because it is free of pollution, high-efficiency, low-noise, low-vibration, fast start-up and long duration. Especially, the awakening in environmental conscience has made the fuel cell a potential power source for use in other fields. The fuel cell has advanced so that the power generation performance is improved with reduced material cost is to make the fuel cell commercialized.
However, the power supply process of the fuel cell is restricted to the reaction mechanism therein. For example, it is hard for the fuel cell to provide large power to the load due to slow oxidation and fuel delivery, which leads to failure of the fuel cell because of insufficient momentary power supply. Moreover, the unstable transient state occurs due to reduced fuel concentration during fuel supply.
In order to avoid momentary high-power demand when the load changes or unstable power supply due to the operation of the fuel cell, a capacitor or a secondary cell module is conventionally used. For example, in Taiwan Patent Pub. No. 200518371, a fuel cell device with a secondary cell is disclosed to reduce power consumption during power conversion by adjusting the output voltage of the fuel cell. Moreover, in Taiwan Patent Pub. No. 200735444, the warm-up time for the fuel cell is reduced so that the power generated will not be wasted. In this technique, the fuel cell and the secondary cell generate hybrid power for various applications. During the operations of the secondary cell, the operation of the secondary cell is insufficient to cause lowered output power when it is over-loaded or has operated overtime. Meanwhile, aging of the over-used fuel cell results from high current and low voltage because there is no mechanism in the secondary cell module to avoid reduced output power. Moreover, there is no cut-off voltage for the secondary cell to get recovered in the prior art when the output power of the secondary cell is reduced.
Therefore, there is need in providing a method of hybrid power management and a system of hybrid power management using the method to overcome the aforementioned problems.